Jessica Watson's family say their thoughts and prayers are with a solo teenage sailor missing in mountainous seas in the middle of the Indian Ocean.

A multi-national search and rescue operation has been launched after emergency beacons onboard 16-year-old Abby Sunderland's boat were triggered when the young American adventurer ran into huge waves hundreds of kilometres from land early this morning.

The Australian Maritime Safety Authority (AMSA) says a Qantas Airbus is heading to the search zone, which is about 3,600 kilometres from the WA coast.

AMSA spokeswoman Carly Lusk says conditions in the search area are poor, with 90 kilometre per hour winds and a six-metre swell.

She says the signals coming from the two beacons Sunderland has activated - one attached to her body and another attached to her boat - suggest she is still in the boat.

She says the crew on board the Qantas jet hope to contact Sunderland by VHF radio once they reach the search area.

"We've got two Qantas flight crews on board, as well as 11 trained air observers from the Western Australian fire emergency services and two Fremantle water police officers," she said.

"Our whole hearts and feelings and prayers go out to her family and whole support team, as well as Abby," she said.

"They've been communicating and we've been communicating with the family as well, so we heard from them this morning, and they are just in the same situation as everyone else, just waiting for information."

She says Jessica knows exactly what is going on.

"Jessica says Abby will be very busy doing all the things she needs to do under those circumstances," she said.

"We had a very similar situation [with Jessica] where the EPIRB went off."

Australian, US and French search and rescue authorities are coordinating several ships in the area, but the nearest ship was more than 500 kilometres away from the search area this morning and is not expected to reach the rescue zone until about midday tomorrow.

Sunderland's father Laurence told ABC Local Radio he last spoke to his daughter during the night (Australian time), but lost contact with her during a satellite phone call.

"She had quite a boisterous night at 60 knots, she was knocked down three times and radar was ripped off the boat, and she had an engine issue," he said.

"She definitely had her cage rattled last night, but after dealing with the engine issue and getting things up and running, everything seemed to be fine.

"We initially thought that the signal was sent automatically from her water-activated EPIRB and that it had been activated during one of her knockdowns.

"As we pulled the paperwork from her EPIRB registration, we learned that the signal had come from her manually-activated EPIRB.

"We were referred to Australian Search and Rescue and while we were on the phone with them another signal came in from her handheld PLB (Personal Locator Beacon). Her water-activated EPIRB has not been activated so we are hopeful that the boat is still upright."

Mr Sunderland said his daughter's yacht may have flipped.

"If indeed the boat is upside down we're hoping that the keel is actually off the boat and giving the boat a positive flotation factor and that she's inside the bubble, safe," he said.

Mr Sunderland expressed his thanks for the Australian search and rescue effort.

Well-equipped

Mr Sunderland said he was still hopeful for his daughter's safety.

"Abby has all of the equipment on board to survive a crisis situation like this," he said.

"She has a dry suit, survival suit, life raft, and ditch bag with emergency supplies. If she can keep warm and hang on, help will be there as soon as possible."

Sunderland began her voyage in her yacht Wild Eyes in January, just months before Jessica Watson completed her around-the-world journey. Watson was also 16 when she set sail, five months older than Sunderland.

Sunderland set sail amid criticism from some in the sailing community that her itinerary was too risky because it would place her in the Indian Ocean during the turbulent Southern Hemisphere winter.

Sunderland's older brother Zac completed his own around the world sailing voyage last year. He arrived back in California last July to a hero's welcome at the end of his 13-month voyage.

Zac Sunderland had been 16 when he set out on the journey, turning 17 in November 2008 before arriving home eight months later.

Watson's journey also began amid a flurry of criticism with many saying she was too young to cope with an around the world journey.

However she completed her journey last month, arriving in Sydney to a hero's welcome met by the Prime Minister, the Premier of New South Wales and thousands of well-wishers.